Fuse cartridges

ABSTRACT

FUSE CARTRIDGES DEVICES COMPRISING RELATIVELY FLAT INSULATING BODY HAVING PARALLEL PERFORATIONS IN WHICH THE FUSIBLE STRIPS ARE DISPOSED, THESE STRIPS CONNECTING ELECTRICALLY TWO END PLATES DISPOSED AGAINST TWO OPPOSED SIDES OF THE INSULATING BODY TO FORM THE TERMINALS OF THE CARTRIDGE. COOLING PLATES ARE APPLIED AGAINST THE PREFERABLY METALLIZED MAJOR FACES OF THE BODY AND MEANS ARE PROVIDED TO DISSIPATE THE HEAT WHICH THE COOLING PLATES RECEIVE FROM THE INSULATING BODY. THESE HEAT-DISSIPATING MEANS MAY BE IN THE FORM OF WATER-COOLED COILS OR OF AIRCOOLED FINS. IN A MODIFICATION THE COOLING PLATES ARE IN HEAT-CONDUCTING CONTACT WITH ONE OF THE END PLATES, ADAPTED TO BE ITSELF APPLIED IN HEAT-CONDUCTING CONTACT AGAINST A COOLED CURRENT-CARRYING BAR.

J. P. CINQUIN FUSE CARTRIDGES Feb. 9, 197-1 2 Sheets-Sheet 1 Filed Sept.16, 1969 Feb. 9, 1971 J p. |NQU|N 3,562,691

FUSE CARTRIDGES Filed Sept. 16, 1969 2 Sheets-Sheet 2 WM bu Int. (:1.110111 85/02 US. Cl. 337-185 9 Claims ABSTRACT OF THE DISCLOSURE Fusecartridges devices comprising relatively flat insulating body havingparallel perforations in which the fusible strips are disposed, thesestrips connecting electrically two end plates disposed against twoopposed sides of the insulating body to form the terminals of thecartridge. Cooling plates are applied against the preferably metallizedmajor faces of the body and means are provided to dissipate the heatwhich the cooling plates receive from the insulating body. Theseheat-dissipatting means may be in the form of water-cooled coils or ofaircooled fins. In a modification the cooling plates are inheat-conducting cont-act with one of the end plates, adapted to beitself applied in heat-conducting contact against a cooledcurrent-carrying bar.

The present invention relates to fuse cartridges used for the protectionof electric circuits or apparatus.

Such fuses cartridges should support in continuous operation thefull-load current of the apparatus which they protect and they shouldblow as soon as this apparatus is liable to be damaged by an overload.These conditions require in practice that the heat produced by theelectric current which flows through the fusible element or elements ofthe cartridge may be easily dissipated. For this purpose it has alreadybeen proposed to realize the insulating body of the cartridge under arelatively flat rec-tan gular form, the fusible elements and thearc-quenching material associated therewith being disposed in parallelperforations extending between two opposed sides of the contour of thesaid body. With such an arrangement the heat flow from an element hasonly to pass through a limited thickness of arc-quenching material andthrough an insulating wall also of limited thickness before reaching theouter surface of the insulating body where it is dissipated byconvection and by radiation. Experience however demonstrates that thecooling effect which is thus obtained is insufficient in many cases andmore particularly when the apparatus to be protected is a semiconductordevice provided with additional cooling means, because theheat-dissipating characteristics of such a device are too such differentfrom those of a fuse cartridge of the kind mentioned.

It is an object of the present invention to provide a fuse cartridgewherein the heat generated by the electric current in the fusibleelements may be dissipated more easily and more rapidly than heretofore.

Another object of this invention is to provide a fuse cartridge whoseheat-dissipating characteristics are substantially similar to those of acooled semi-conductor device protected by the said cartridge.

According to the present invention in a fuse cartridge comprising asubstantially flat insulating body having parallel perforationsextending between two opposed sides of the contour of the said body,fusible elements disposed in the said perforations together witharc-quenching material, and electrically conductive end plates disposedUnited States Patent 3,562,691 Patented Feb. 9, 1971 against the saidopposed sides and electrically connected with each other by the saidfusible elements, heat-conducting cooling plates are applied inheat-conducting contact against each of the major faces of theinsulating body, means being provided for dissipating the heat which thesaid cooling plates receive from the said body, and one at least of thesaid end plates being spaced from the said cooling plates.

The heat dissipating means may be formed of tubes or passages associatedwith or provided in the cooling plates and through which a cooling fluidis circulated, or of aircooled fins carried by the said cooling plates.In the case of a fuse cartridge intended to be mounted on a cooledcurrent-carrying bar, the cooling plates may be integral with the one ofthe end plates of the cartridge which is adapted to be applied againstthe bar, the said end plate playing the role of the saidheat-dissipating means.

In order to reduce the resistance to the heat flow between theinsulating body of the cartridge and the cooling plates, the major facesof the body are preferably metallized, the metallization terminatingshort of at least one of the opposed sides against which the end platesare applied, and the cooling plates are soldered to the metallizedfaces. The metal used for the metallization is preferably a fusiblemetal or alloy such as tin.

In the accompany drawings:

FIG. 1 is a side view of a twin fuse cartridge unit according to theinvention, one of the elementary cartridges being illustrated inlongitudinal section.

FIG. 2 is a front view thereof with parts in section.

FIG. 3 is a plan view of the unit illustrated in FIGS. 1 and 2.

FIG. 4 is a horizontal section of a modified metallic cooling plate.

FIG. 5 is a perspective view of the insulating body of a fuse cartridgebefore metallization of its major faces.

FIG. 6 is a longitudinal section of the insulating body with the coolingplates soldered to the metallized faces.

FIG. 7 is a longitudinal section of a cartridge body equipped withcooling plates having air-cooled fins.

FIG. 8 very diagrammatically illustrates the arrangement of theair-cooled fins in a twin fuse cartridge unit.

FIG. 9 is a side view of a fuse cartridge adapted to be carried by acooled current-carrying bar.

FIG. 10 is a plan view thereof.

Referring to FIGS. 1 to 3, a twin fuse cartridge unit is formed of twoelementary cartridges, generally referenced A and B, disposed above eachother, and of three cooling devices C, D and E associated therewith.

Each elementary fuse cartridge comprises a heat-resistant insulatingbody 1 (preferably made of a ceramic material of high heat conductivity)having the form of a relatively thick rectangular plate provided withthree parallel perforations 1a of elliptic cross-section which extendbetween two opposed sides of the rectangular contour of body 1, with themajor axis of their cross-section parallel to the major faces of thesaid body. A fusible strip 2 is disposed in each perforation 1a, thisstrip being embedded in a mass 3 of a pulverulent arc-quenching materialwhich fills the perforation. As illustrated strips 2 are folded inrectangular zig-Zag fashion, i.e. they comprise alternate upper andlower straight horizontal portions connected by short vertical portions.Each one of the ends of the strips is clamped between the correspondingside of body 1 and a metallic end plate 4 having a horizontallyextending lug 5 adapted to form one of the terminals of the unit. Asshown each end plate 4 extends horizontally across the full width of theunit and its height is such that it is common to the two elementarycartridges A and B. These end plates are suitably secured to body 1 ofeach elementary cartridge, as for instance by screws 6, body 1 beingformed for this purpose with corresponding screw-threaded holes 1b (FIG.1).

The above-mentioned cooling devices C, B and E are respectively mountedon the upper face of elementary cartridge A, between the lower face ofcartridge A and the upper face of cartridge B, and against the lowerface of cartridge B. Each device comprises two copper cooling plates 7and 8 between which is disposed a heat-dissipating copper tube folded onitself in the form of four parallel branches, the said tube beingsoldered to plates 7 and 8.

The whole unit is clamped by means of bolts 10.

In operation a cooling fluid, such as water, is circulated through tubes9 in order to evacuate heat collected by the copper plates which are incontact with the major faces of the elementary cartridges (or moreexactly of the insulating bodies 1 thereof). Since the resistance to theheat flow between the fusible strips and the said faces is relativelylow owing to the small thickness of arc-quenching material interposedbetween each horizontal portion of the strips and the adjacent wall ofthe perforations, and also to the small thickness of insulating materialbetween this wall and the adjacent outer surface of body 1, thetemperature of the strip does not rise dangerously in permanentoperation under full nominal load. Moreover the heat-dissipatingcharacteristics of the fuse cartridge unit may be similar to those ofwater-cooled semi-conductor devices with which such units may beassociated FIG. 4 shows another embodiment of a cooling device for afuse cartridge unit of the kind of FIGS. 1 to 3. This device comprises athick copper plate 11 in the thickness of which a number of longitudinalpassages 11a (three in the example shown) have been drilled, thesepassages being connected by transverse passages 11b. By obturatingappropirate portions of these passages by plugs such as 12, it ispossible to provide a single path for the flow of a cooling fluidbetween an inlet and an outlet.

It is of course important to realize a good heat-conducting contactbetween the major faces of the insulating body 1 of each elementarycartirdge A or B and the corresponding cooling plate such as 7, forinstance. This is preferably obtained by metallizing the said faces, asfor instance by spraying thereon molten metal droplets by means of ametallizing pistol. F or this purpose a protective covering 20 (FIG. 5)is first applied on each major face of body 1 in the vicinity of thesides thereof onto which the end plates 4 are ubsequently to be secured.This covering is conveniently realized by wrapping an adhesive strip onbody 1, the width a of this strip corresponding to the safe distancewhich is to be maintained between each cooling plate such as 7 and theadjacent end plate 4 for avoiding short-circuits. The exposed portion ofeach major face is then cleaned by sand-blasting and tin or anothersimilar easily fusible metal or alloy is sprayed thereon in order torealize a first metallic layer 21 (FIG. 6) firmly attached to theinsulating material. A copper plate 7 which has been carefully cleanedas required, is then applied against each layer 21 and it is heated upto the melting point of the metallic layer 21. The plate 7 is thussoldered to the metallized face of the insulating body. The heatingoperation may be effected in an appropriate oven, plates 7 (togetherwith tubes 9 and plates 8) being maintained against body 1 byappropriate springs. During this soldering operation, owing to thepresence of the strip or covering 20, no molten metal can flow towardthe sides of the insulating body which will thereafter receive the endplates 4. The strips or coverings 20 are then removed and the fusecartridge may be mounted in the usual way.

It is obvious that the metallization could be performed by means of anydesired metal, as for instance copper, the cooling plates beingthereafter soldered to the metallic layer thus realized.

While FIG. 6 only shows a single fuse cartridge, it is obvious that thesame procedure may be applied in the 4 case of multiple cartridge units,as for instance to the twin unit of FIGS. 1 to 3.

In the embodiment of FIG. 7 the cooling plates, here refrenced 22, areprovided with air-cooled heat-dissipating fins 23 which may for instancebe soldered to plates 22. In a modification each plate 22 may be casttogether with the corresponding fins 23.

In the case of a multiple fuse cartridge unit the facing fins 23a of theelementary cartridges may be interdigitated, as shown in FIG. '8, theirnumber being preferably reduced with respect to the fins 23 of the outercooling plates of the unit, as illustrated. As in the construction ofFIGS. 1 to 3 the unit preferably comprises a single pair of end platesfor the insulating bodies 1A and 1B of both elementary cartridges.

In FIGS. 9 and 10 the fuse cartridge is adapted to be mounted on amassive current-carrying bar 24 which is itself cooled in anyappropriate manner, as for instance by inner water circulation aswell-known in the art. The cooling plates 25 carried by the insulatingbody 1 of the cartridge are integral with one 26 of the end plates ofthe cartridge and this end plate is applied in heat-conducting contactagainst the current-carrying bar 24. In the example illustrated the endplate 26 carries two screwthreaded rods 27 which are passed throughholes provided in bar 24, their protruding ends receiving clamping nuts28.

It will be understood that the heat collected by cooling plates 25 flowstowards end plate 26 and is transferred to bar 24 from which it isevacuated by the cooling agent.-

Of course cooling plates 25 and end plate 26 should be thick enough foroffering no appreciable resistance to the heat flow. It is also oviousthat the cooling plates 25 could be realized in the form of separateparts soldered to the end plate 26.

I claim:

1. A fuse cartridge comprising:

a substantially flat insulating body having two opposed sides and twomajor faces, said body 'being formed with substantially parallelperforations extending between said opposed sides;

electrically conductive end plates disposed against said opposed sides;

fusible elements disposed in said perforations to electrically connectsaid end plates with each other;

heat-conductive cooling plates applied in heat-conducting contactagainst said major faces of said insulating body, said cooling platesterminating short of one at least of said end plates;

and means to dissipate from said cooling plates the heat which theyreceive from said insulating body.

2. In a fuse cartridge as claimed in claim 1, said major face of saidinsulating body being metallized with the metallization terminatingshort of said one of said end plates, and said cooling plates beingsoldered to said metallized major faces.

3. In a fuse cartridge as claimed in claim 1, said heatdissipating meansbeing in the form of fluid-cooled tubes in heat-conducting contact witheach of said cooling plates.

4. In a fuse cartridge as claimed in claim 1, each of said coolingplates being formed with inner passages for a cooling fluid so as toform by itself said heat-dissipating means.

5. In a fuse cartridge as claimed in claim 1, said heatdissipating meansbeing in the form of air-cooled fins carried by said cooling plates.

6. In a fuse cartridge as claimed in claim 1, each of said perforationscontaining a single fusible element, said element being in the form of astrip having successive pairs of folds substantially at right angesalternately in one and in the other direction so as to determinealternate upper and lower horizontal portions connected by verticalportions, and said strip beig emnbedded in a mass of arc-quenchingmaterial.

7. A fuse cartridge adapted to be mounted on a cooled current-carryingbar, said fuse cartridge comprising:

a substantially flat insulating body having two opposed sides and twomajor faces, said body being formed with substantially parallelperfortions extending-between said opposed sides;

a first and a second electrically conductive end plates disposed eachagainst one of said opposed sides, with aid first end plate arranged tobe applied in heatconducting contact against a cooled current-carryingbar;

fusible elements disposed in said perforations to electrically connectsaid first and second end plates with each other;

and heat conductive cooling plates applied in heat-conducting contactagainst said major faces of said in- 15 6 9. In a fuse cartridge asclaimed in claim 7, said major faces of said insulating body beingmetallized with the metallization terminating short of said second endplate, and said cooling plates being soldered to said metallized. majorfaces.

References Cited UNITED STATES PATENTS 1,696,605 12/1928 Hollnagel337280 2,326,257 8/ 1943 Schmidt 337166 2,871,314 1/1959 Swain 337--1583,453,579 7/1969 Cinquin 337161 FOREIGN PATENTS 23,514 2/1913 GreatBritain 337-222 HAROLD BROOME, Primary Examiner US. Cl. X.R.

